/*
 *                               POK header
 *
 * The following file is a part of the POK project. Any modification should
 * be made according to the POK licence. You CANNOT use this file or a part
 * of a file for your own project.
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2021 POK team
 */

/* e_fmodf.c -- float version of e_fmod.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
 * __ieee754_fmodf(x,y)
 * Return x mod y in exact arithmetic
 * Method: shift and subtract
 */

#ifdef POK_NEEDS_LIBMATH

#include "math_private.h"

static const float one = 1.0, Zero[] = {
                                  0.0,
                                  -0.0,
};

float __ieee754_fmodf(float x, float y) {
  int32_t n, hx, hy, hz, ix, iy, sx, i;

  GET_FLOAT_WORD(hx, x);
  GET_FLOAT_WORD(hy, y);
  sx = hx & 0x80000000; /* sign of x */
  hx ^= sx;             /* |x| */
  hy &= 0x7fffffff;     /* |y| */

  /* purge off exception values */
  if (hy == 0 || (hx >= 0x7f800000) || /* y=0,or x not finite */
      (hy > 0x7f800000))               /* or y is NaN */
    return (x * y) / (x * y);
  if (hx < hy)
    return x; /* |x|<|y| return x */
  if (hx == hy)
    return Zero[(uint32_t)sx >> 31]; /* |x|=|y| return x*0*/

  /* determine ix = ilogb(x) */
  if (hx < 0x00800000) { /* subnormal x */
    for (ix = -126, i = (hx << 8); i > 0; i <<= 1)
      ix -= 1;
  } else
    ix = (hx >> 23) - 127;

  /* determine iy = ilogb(y) */
  if (hy < 0x00800000) { /* subnormal y */
    for (iy = -126, i = (hy << 8); i >= 0; i <<= 1)
      iy -= 1;
  } else
    iy = (hy >> 23) - 127;

  /* set up {hx,lx}, {hy,ly} and align y to x */
  if (ix >= -126)
    hx = 0x00800000 | (0x007fffff & hx);
  else { /* subnormal x, shift x to normal */
    n = -126 - ix;
    hx = hx << n;
  }
  if (iy >= -126)
    hy = 0x00800000 | (0x007fffff & hy);
  else { /* subnormal y, shift y to normal */
    n = -126 - iy;
    hy = hy << n;
  }

  /* fix point fmod */
  n = ix - iy;
  while (n--) {
    hz = hx - hy;
    if (hz < 0) {
      hx = hx + hx;
    } else {
      if (hz == 0) /* return sign(x)*0 */
        return Zero[(uint32_t)sx >> 31];
      hx = hz + hz;
    }
  }
  hz = hx - hy;
  if (hz >= 0) {
    hx = hz;
  }

  /* convert back to floating value and restore the sign */
  if (hx == 0) /* return sign(x)*0 */
    return Zero[(uint32_t)sx >> 31];
  while (hx < 0x00800000) { /* normalize x */
    hx = hx + hx;
    iy -= 1;
  }
  if (iy >= -126) { /* normalize output */
    hx = ((hx - 0x00800000) | ((iy + 127) << 23));
    SET_FLOAT_WORD(x, hx | sx);
  } else { /* subnormal output */
    n = -126 - iy;
    hx >>= n;
    SET_FLOAT_WORD(x, hx | sx);
    x *= one; /* create necessary signal */
  }
  return x; /* exact output */
}

#endif
